DESCRIPTION: The reservoir of cells harboring latent HIV-1 precludes a cure of infection by existing anti-HIV drugs. The best described latent reservoir is that of long-lived memory CD4+ T cells. Multiple mechanisms are thought to be involved in HIV latency in these cells: repressive chromatin; transcriptional interference by cellular genes; limiting levels of cellular transcriptio factors, especially the transcriptional elongation factor termed P-TEFb. We propose to develop methods to selectively up-regulate P-TEFb in resting CD4+ T cells, as well as to demonstrate associations in vivo between regulation of P-TEFb and HIV latency. In the R21 phase of the proposed research, we will determine if selective up-regulation of P-TEFb, either alone or in synergy with other latency activating agents, can reactivate latent HIV in a primary CD4+ T cells model of latency. In the R33 phase of the work, we will determine if selective up-regulation of P-TEFb, either alone or in combination with other agents, can reactivate latent HIV in patients' samples. To investigate P-TEFb and HIV latency in vivo, we will utilize immunohistochemistry (IHC) and RNA in situ hybridization (ISH) to examine lymph node and brain samples from HIV- infected individuals, both before and after anti-viral therapy. The proposed work has the potential to establish an association in vivo between the regulated expression of P-TEFb and HIV replication and latency. Importantly, the proposed work has the potential to establish that selective up-regulation of P-TEFb is a feasible strategy to reactivate latent HIV in vivo.